Electronic switch



Feb. 13, 1951 K. BLAKE I ELECTRONIC SWITCH Filed NOV. 19, 1945 SWEEP GENERATOR KENNETH BLAKE Patented Feb. 13, 1951 ELECTRONIC swrron Kenneth Blake, Washington, D. 0., assignor to Minister of Supply in His Majestys Government of the United Kingdom of Great Britain and Northern Ireland, London, England Application November 19, 1945, Serial No. 629,669

Applications often arise in echo-ranging and other electronic apparatus wherein a video or an audio signal is to be switched from one signal channel to another responsively to the ac- .tion of a mechanical switch. An example is in systems employing'antenna-lobe switching, in which the video output of the receiver should be switched from one indicator component to another simultaneously with the operation of the lobing switch in the antenna apparatus. Switching a video or an audio signal by mechanical means often is unsatisfactory in such .a'pplications because of distortion of the video signal caused by large shunt capacitances in the mechanical switch and the cables leading thereto. It is accordingly one object of this invention to obviate the aforementioned difiiculties and to provide electronic means for effecting rapid sigpal-current switching in response to the action pf a mechanical switch, without distortion of the waveform.

The invention will be better understood by reference to the following specification taken in connection with the accompanying drawing in which the single figure shows schematicallyone embodiment of the invention as incorporated in ,the cathode-ray tube indicator device of an echo-ranging and object detecting system.

;; Referring more specifically to the drawing,;a cathode ray tube It] is indicated schematically by'the circular outline within which only'the beam deflection plates are shown. Thus, the plates producing verticalbeam deflection are ,denoted respectively H and I2 while the plates producing horizontal beam deflection are numbered |3 and I4. --The vertical beam deflection plates II and l2 are connected to a sweep generator 5, shown in block form, which produces systematic vertical deflection of the electron ;beam. A conventional D.C. restoration and polsitioning circuit, comprising diode tubes 60 and J0, D.C.-source B5, and the resistors and condensers associated therewith, is connected to the fdeiiection plates I3 and I4; this :circuit'maintains a stable horizontal beam position except when signals are fed to one of the horizontallydeflecting' plates l3 and I4. Tube .50 is the final video amplifier tube of a receiver (not shown), the plate 49 of this tube connected .to D.C. source'52 through load g r 'esistor 6| and also connected to thecathodes of 9 Claims. (01. 250-27) diode tubes 20 and 30. The plate 2| of diode 20 is connected through coupling condenser IE to deflection plate IS; the plate 3| of diode 39 is connected through coupling condenser H to defiection plate l4. The plate 19 of triode tube 88 is connected to the plate 2| of diode 20; load resistor 8| is connected between the plate 19 of tube and positive D.C. voltage source 85. The plate 95 of tube 90 is connected to the plate 3| of diode 30; and load resistor 9| is connected between the plate 95 of tube 99 and positive D.C. source 85.

The cathodes of tubes 80- and 99 are connected together and are connected to ground through biasing resistor 89. By-pass condenser 88 is connected in parallel with resistor 89. Resistors B3 and 84 are connected in series between the control grid of tube 88 and its cathode. The grid of tube 89 is by-passed to ground by con denser 82. Resistors 93 and 94 are connected in series between the control grid and cathode of tube 98; the grid of tube 90 is by-passed to ground by condenser 92.

Switch withinv the block shown in broke lines is a mechanical switch. In this apparatus is operating on one antenna lobe, and with con] tact 4 while the system is operative on the other lobe. Contact 3 is connected to the junctionof resistors 83 and 84. Contact 4 is connected to the junction of resistors 93 and 94. l Contact. 2 is grounded.

The negative sides of all the D.C. sources shown may be considered grounded. The potential of positive source should be substantially greater than the D.C. potential at the plate 49 of tube 50. Typical values employed in a practical construction were 300 volts at the plate of tube 50 and 400 volts at DC. source 85,

In describing the operation of the invention, it will be first assumed that switch is in the position wherein contact 3 is grounded andcontact 4 is open. Under these circumstances tube 90, having its grid at cathode potential, will conduct and tube 80, the grid of which is at ground potential, will be cut off. (The current drawn by tube flows through resistor 89 and raises the cathode of tube 8|] sufficiently above ground to cutofi current 80.) Since tube 90 conducting, a large voltage drop occurs in resistor 9|, and the plates 95 and 3! of tube 90 and diode 30, respectively, are at a low voltage, i. e., much less positive than the voltage at the cathode of diode 30. In consequence, therefore, no current fiows in diode 30 and no video signals reach defiection plate M of cathode-ray tuber ill; Tube." 80 being nonconducting on the other hand, its plate voltage rises to a value more positive than that of the cathode of diode 2B. In consequence;

a direct current flows from D.-C. source--85,

through load resistor BI, and diode 20 to the plate 49 of tube 50. and the resulting potential at the plates 21 and 19 of tubes 20 and 8D, respectively; is proportional. to the instantaneous plate voltage of tube 59.

The magnitude of this-'current, 1

means to pass signals through to the first channeL'said control means being operative when the switching means is in another operating position to apply a blocking bias voltage to the first Thus video signals appearing at the plate. of tube 50 are reproduced at the plate of diode 2e and applied through condenser IE to deflection plate l3. If the video signal consists of negative pulses, l

the application of the video voltage to deflection plate i3 would result in beam deflection away from that plate or to the right as the cathode ray tube is viewed in the drawing.

Now suppose the antenna lobe switch shifts to its other position, and in synchronism therewith contact 2' of switch I is shifted so as to ground contact 4 and leave contact 3 open. The tubes 80 and 90, in this instance, interchange roles; tube 80 conducts heavily and tube 9!! is cut off. The plate voltage of tube 80 drops sharply and blocks any further transmission of signals through diode 20. The plate-voltage of tube 99 meanwhile rises, at a rapid rate. When it reaches the potential of thecathode of diode 3% that diode starts to conduct and signal transmission proceeds as before, except that signals are now applied to deflection plate 23', where they cause beam deflection in tube ID in the opposite direction. The result is the type of ranging data prerect currents andtherefore can be made long as necessary without distorting the waveform of the video currents which are switched electronically from deflection plate 53 to deflection plate M. In practical installations switch I must usually be situated near the antenna of the ranging system at a considerable distance from cathode ray tube l0, and cable capacitances would se-- riously attenuate the high frequency components of the video currents were those currents carried to and from switch I. v v v The advantage of this system over a mechanical rel'ay'system is that the capacitances inherent in this invention are very small and switching transients arev ended withinone or'ftwo milliseconds after a switching operation, a much shorter time thanca reliably be achieved by a mechanical relay.

It will be understood that the embodiment of the invention herein shown and described is'exemplary only, and that the scope of the invention is to be determined by reference to the pended claims.

What is claimed is: l. In combination, a signal source; first and "second signal channels; a first unidirectional I unidirectional electronic means and to allow the second unidirectional electronic means to pass signalsv through to the second channel.

2. In combination, a signal source; first and I second signal channels;v a first diode means coupling the signal source to the first channel; a second diode means coupling the signal source to the second channel; -aswitch having first and second states; and control means responsiveto the switch operative when the switch is in the first state to apply a blocking bias voltage to the second diode means'and to allow the first diode means to pass signals through to the first cha nnel, and operative when the switch is in-the second state to apply a blocking bias voltage to the first diode means and to allow the second diode means to pass signals through to the second channel. 7

I 3. In combination, a signal source; first and second signal channels a first diode means pling the signal source to the first channel; is second diode means coupling the signal source 'to the second channel; a first control tube hav' 'ing a cathode, an anode and a grid; a second con-'- trol tube having a cathode, an anode and. ages;

means coupling the anode of the first control tube:

to the first diode; means coupling the anode of the second control tube to the second diode;'--a switch having first and second states; and means coupling the grids of the control tubes to' the switch means operative when the switchis' -in :thefirst state to bias the grid of'the first-control tube to render the first diode means conduct ing and to bias'the grid of the secondcontr'ol tube to block the second diode means, and operative when the switch is in the second-s-tate-to bias the grid of the second control tube to render the second diode means conducting and to bias the grid of the first control tube to block 'th'efirst :diode means. 4. In combination, a signal source; first and second signal channels; a first diode meanscow -pling' the signal source to the first channel; -'-a second diode means coupling the-signalsourceto the second channel; a first control tube having a cathode, an anode, and a grid; asecondi can 'trol tube having a cathode, an anode, and a gr d means coupling theanode of the first control tube to the first diode means; means coupling the anode of the second control tube to the second diode means; a voltage source; impedance-means connecting the anode of the first control tube to the voltage source; impedance means connecting the anode of the second tube to thevol'tage source; impedance means coupling the "grid of "the first tube to its cathode; impedance means coupling the grid of the second tube to ,itscath ode; means biasing the cathodes of both control ftubes at a bias voltage relative to ground fa switchmeans having first and-second statesj anfld means-operative to lacethe gridof'thefii'st' control tube at ground potential when the switch is in the first state and operative to place the grid of the second control tube at ground potential when the switch is in the second state.

5. In combination, a signal source, a plurality of signal channel's, diode means coupled between said source and each of said channels, each of said diode means responsive to an unblocking bias to establish a circuit between said source and the channel coupled thereto and responsive to a blocking bias to isolate said source from the channel coupled thereto, electronic control means operative to apply an unblocking bias to any one of said diode means and to simultaneously apply a blocking bias to the remainder of said diode means and switch means controlling said control means so that a circuit may be established between source and any preselected one of said channels.

6. In an apparatus for selectively controlling application of a signal source to any one of a plurality of signal channels, electronic coupling means positioned between said source and each of said channels, each of said electronic coupling means responsive to an unblocking bias to establish a circuit between said source and the channel associated therewith, control means operable to apply an unblocking bias to any one of said electronic coupling means and selectively operable switch means to control said control means so that an unblocking bias may be applied to a preselected one of said electronic coupling means.

7. In an apparatus for selectively controlling application of a signal source to any one of a plurality of signal channels, electronic coupling means positioned between said source and each of said channels, each of said electronic coupling means responsive to an unblocking bias to establish a circuit between said source and the channel associated therewith and responsive to a blocking bias to isolate said source from said associated channel, controlmeans operable to apply an unblocking bias to any one of said electronic coupling means and to simultaneously apply a blocking bias to the remainder of said electronic coupling means and selectively operable switch means to control said control means so that a circuit may be established between said source and any preselected one of said signal channels.

8. In an apparatus for selectively controlling the application of a signal source to either of two signal channels, electronic coupling means positioned between said source and each of said channels responsive to an unblocking bias to establish a circuit between said source and the channel associated therewith and responsive to a blocking bias for isolating said source from said associated channel, control means operable to apply an unblocking bias to either of said coupling means and to simultaneously apply a blocking bias to the other of said coupling means and selectively operable switch means to control said control means so that a circuit may be established between said source and a preselected one of said signal channels.

9. In combination, a signal source, a plurality of signal channels, a plurality of uni-directional discharge devices each including a cathode and an anode connecting said source to said channels with the cathode of each of said devices connected to said source and with the anodes thereof connected to separate channels of said channels, means applying positive bias to the oathodes of said devices, and selectively operable means applying positive bias greater than the positive bias applied to said cathodes to any one of said anodes for selectively coupling said signal source to any one of said signal channels.

KENNETH BLAKE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,080,082 Loth May 11, 1937 2,189,317 Koch Feb. 6, 1940 2,226,930 Hefele Dec. 31, 1940 2,279,021 Cooper Apr. 7, 1942 2,456,666 Agate Dec. 21, 1948 OTHER REFERENCES A Scale of Two High Speed Counter Using Hand Vacuum Triodes, by W. B. Lewis, vol. 37, Proceedings of the Cambridge Philosophical Society, 1937, pages 549-558. 

